Multiwave band superheterodyne receiver



lnven-t-o-r WA R, KOCH Filed May 29, 1936 yMULTIWANE AND SUPERHETERODYNE RECEIVER March 14, 1939.

UNITED STATES MULTIWAVE BAND' SUPERHETERGDYNE RECEIVER Winfield R. Koch, Merchantville, N. J., assigner to Radio Corporation of America, a, corporation of Delaware Application May 29, 1936, Serial No. 32,416 7 Claims. (Cl. Z50- 20) The present invention relates to la multi-wave forme-r l together with shunt trimmer capacitors band superheterodyne receiver, and has for its represented by the capacitorl is removable from primary object to provide a receiver of' that charthe circuit through the medium of the contacts 9 acter'which provides for simultaneous wave band and il, and may be replaced by other similar change in both the intermediatefrequency and coupling devices 20, 2i and 22 which may be 51;.1

signal selecting circuits, to maintain a predetermoved progressively into connection at the con.- mined desired relation between the selected intertacts 9 and H in the order named, as indicated mediatefrequency andthe lowest frequency in a by the ldotted' lines 23 and 24. selected receiving band of frequencies. The'coii unit 2li is located in the input circuit 10 It is also an object of the present invention to of an intermediate frequency amplifier device 25 1"'0-1i provide a Ymulti-wave band superheterodyne reand is tuned by a shunt capacitor 26 in the first ceiver having means for adjusting the tuning of intermediate frequency input circuit.

intermediate frequency amplier circuits for a In the present example andas a preferred' ardiffering wave-band response corresponding to rangement, the unit 22 may be tuned to respond to tunable signal selecting or radio frequency cirbe tuned to respond to an intermediate frequency cuits'of the receiver, whereby an improved image of 550 kc., and the unit 253 may be tuned to reffrequency ratio and a desired degree of selectivity spond to an intermediate frequency of 1500 kc. is obtainable in differing wave bands covering a The unit 'l is tunable through a frequency range wide frequency or wave length range of operation of 4500 to 13,500 kc, by the tuning capacitor |2 2y for the receiver. thereby providing for operation of the receiver It is a still further object of the present invenin three frequency ranges, which-may be desigtion, to provide a superheterodyne radio receiver, nated as shown below: wherein a desired frequency relation between the predetermined wave band adjustments in the an intermediate frequency of 175 kc.,unit 2l may 1*'5- 25 intermediate frequency and the lowest frequency Band IF RF 25.

inY a selected frequency band of operation is maintained for substantially all selected frequency f bands' of operation, and wherein the radio fre- A 55041500 quency coils and intermediate frequency coils B 550 15004500V o 1500 450043500 Kilocycle Kilocycle 175 constituting portions of the tuned signal circuits 39:;

may be used progressively, the coils for an intermediate frequency amp-lifier covering one fre- These frequency ranges are ChOSGn by Way 0f quency band of operation for the receiver, being @Kmme and represent any Suitable number' 0f used as the radio or high frequency coils in the tuning ranges which may be ChOSBn t0y @overa receiving circuits for the next lower frequencyr palticlllar'wd tuning range for a multi-Wave 355;

band of operation. band receiver.

The invention will, however, be' better under- It Will be seen that with this arrangement, the stood fromfthe following description, when conltemedate TSliU-eny COllPlrlg Unit 2U, When sideredv in connection with the accompanying moved into the pOstOn OCCllDied by Coupling unit 40 drawing, and its scope will be pointed out in the 'i is tuned to the lowest frequency in the next 40j appended Claims, lower frequencyv band, which is the B band, and In thedrawing, the figure-is a'schematic circuit thev unit 'l is out of operation. At the same time, diagram of a multi-wave band superheterodyne the" @Clipline Unit 2i S- mOVGd iilt the' Position receiver embodying the invention occupied by the coupling unit 2i! and is tuned to Referring to the drawing, the radio receiving 550y kc. whereby fOr the B 'Da-nd an intermediate" 4%51 system illustrated comprises a radio frequency rqllelly 0f 550 ki iS DlOVded, Whilethe input amplifier tube 5 coupled t0 a, Signal input; circuit O1 receiving Circuit is tunable from 1500 kc'. 130 through a removable coupling unit 1, lcompris- 4500 kc. ingn a, primary winding 8 connected through'conn a Similar manner, the C011 22 may be moved v mais ewan the input circuit t and having a into the positionk occupied by the Coil 26 shown s' tuned secondary winding Il) connectedthrough in thedrawing, whlethe couplingl unit 2| will contacts H with a shunt variable tuning capacithen occupy, by progressive movement, the positor l2 and the signal input'grd I3 of the tube 5. tion occupied by the coupling unit 'l shown in the A grounded common chassis or return circuit lead drawing. The coupling unit 2i being responsiveto sei-is indicated at I4. Thecoupling device or trans- 550 kc. permits tuning through the A band-from which the coupling units 550 kc. to 1500 kc. while the coupling unit 22 responsive to 175 kc. provides the intermediate frequency amplifier input coupling unit.

It will be seen that the frequency relation is such that the intermediate frequency is maintained at a value substantially one-third of the lowest frequency in the high frequency or radio frequency receiving band to be covered. It has been found that this relation of frequencies provides for less difficulty from image and other responses in the higher frequency bands, .and accordingly the present tuning range adjustment permits this ldesirable ratio to be maintained over a relatively wide frequency coverage.

Oscillator, rst detector and other intermediate frequency amplifier circuits are similarly tuned and adjusted to cover the same corresponding frequency bands, in accordance with the system thus far described. In the present example, the oscillator and first detector are combined in one device 30, known as a penta-grid converter having a signal input grid 3l, an oscillator grid 32, .an oscillator anode electrode 33, anl output anode electrode 34, and a cathode 35.

The signal input grid is further provided with a screen 3d, and is connected in circuit through contacts 'with a tuned coupling unit or transformer 38 which in turn is connected through contacts 39 with the output circuit llt! of the radio frequency amplier tube 5. The grid circuit is tunable through the same frequency range as the radio frequency amplifier unit 1, by means of a second variable tuning capacitor 4l corresponding to the tuning capacitor l2.

The oscillator circuit comprises a tuned coupling unit d3, the primary Il@ of which is connected through contacts 45 with the anode electrode 33, and the secondary G6 of which is connected through contacts 41 with the oscillator grid 32 which is pro-vided with the usual gridV leak and capacitor 48, 49. The oscillator circuit is tuned by suitable means comprising a variable capacitor 5U and a series tracking capacitor 5l, the three capacitors l2, 4i and 5B normally being connected together for simultaneous uni-control operation.

The detector-oscillator output anode 34 is connected through a lead 55 with the intermediate frequency input coupling unit 2G through contacts indicated at 56. The oscillations set up in the device result from electronic coupling between the oscillator frequency and the incoming signal frequency as is known and understood, to provide the desired intermediate frequency of 1500 kc. The oscillator coupling unit 43 therefor is tunable to a frequency differing from that to .3l and 38 are tuned, by the amount of the selected intermediate frequency.

With this arrangement, the coupling unit between the radio frequency amplifier 5 and the first detector 3Q may be replaced in the same manner as coil 'switching arrangement hereinbefore described, by a coupling unit G3 forming the second stage coupling unit of the intermediate frequency amplifier between the first stage intermediate frequency amplier 25 and a second stage or detector device indicated at 59. In the present example, the device 59 is a second detector and is provided withV suitable output coupling means 62-.and output circuit S3 for supplying audio frequency signals to an amplifier 64 and a suitable output device such as the loudspeaker B5. The coupling units l and 38 are substantially the same in tuning range and frequency response,

and likewise, the coupling units 20 and 60 are the same since they are tuned to the same intermediate frequency, the capacitor 26 and a capacitor 6l being used to adjust the coupling units to the desired resonance point for use in the intermediate frequency amplifier.

For the second stage or detector B and A bands, coupling units indicated at 66 and 61 are provided to correspond to the first stage coupling units 2| and 22, respectively, and are tuned respectively to the same frequencies. The wave band changing operation therefor is the same as that described for the first stage intermediate frequency amplifier and the input circuit of the receiver or radio frequency stage.

The switching contacts for the coils or tuning units 50, 66 and l in the intermediate frequency amplifier are indicated at 10 and 1I, and in connectionV with the coils 2U, 2l andV22, the output contacts therefor are indicated at l2. The coils l, E6, 2l and 22 are therefore moveable along the line 23 and 24 to carry the coils 2G, 2l and 22 progressively through the intermediate frequency contacts 55 and 'l2 and the high frequency or signal input contacts S and I l. In the present example, the couplingV unit 22 r-ests at the position `occupied by the unit 2li between the contacts 56 and l2 for the A band operation in the same manner that the coil 'a' initially rests in the position shown between the contacts 9 and II and does not make Contact with any other circuits in the three band arrangement shown. Other similar bands may be provided by additional coupling units movable into contact as described for those shown.

Similarly the coils or coupling units 38, 60, 66 and Si are movable in the direction indicated by the dotted lines i3 and 74, to effect the same changes simultaneously with the' wave band changes above described.

Since the oscillator comprises a separate circuit tunable to a differing frequency, separate coupling units to be substituted for the unit 43 are indicated at 58 and 69. It will be noted that for the A band a coupling unit for the oscillator is not requiredsince there is no corresponding stage in the intermediate frequency amplifier with which the oscillator coils are progressively interchangeable.

From the foregoing description it will be seen, that in a superheterodyne receiver having a tunable radio frequency amplifier stage and a tunable first detector or mixer stage coupled thereto, andV responsive to the same selected signal frequency range, and having an intermediate frequencyV utilization of the intermediate frequency amplier coils or coupling devices as the signal input andY mixer tuning units in the next lower frequency receiving band is possible a desirable arrangement resulting in a saving of coupling units or windings and simplifying the switching operation. The latter operation m-ay be made progressively by any suitable mans for carrying the various coupling units progressively between the contacts of the fixed circuits to be associated therewith. The number of oscillator coils is one less than the number required for the other circuits to ce provided in the switching operation.

This system also. has the further advantage that there is less radiation from the receiving system because the antenna circuit or input circuit is tuned to a greater frequency difference from the oscillator and there is less tendency for the oscillator frequency to be affected by the tuned circuit which supplies signals to the first detector or frequency changer device, particularly when the oscillations and signals are mixed electronically as in the present example.

Furthermore, the total number of component circuit elements required is smaller than for the usual type of multi-wave band receiver wherein the intermediate frequency amplifier if adjusted in frequency, requires a separate series of coupling units or tuning means.

The main advantage, however, lies in the fact that desirable frequency relation between the intermediate or signal frequencies and the intermediate frequency may definitely be maintained throughout a relatively wide tuning range of operation comprising a plurality of frequency bands, without requiring a plurality of intermediate frequency amplifiers and without resorting to a compromise in the intermediate frequency for reasonable performance in a plurality of different signal receiving bands.

A fixed intermediate frequency is not only too high in frequency for best selectivity and tracking in the broadcast band but is too low in frequency and too selective for receiving short Waves. With the present arrangement this disadvantage is overcome without introducing the additional disadvantage of complicated coils and additional circuit components and tuning means.

In the present system, wherein the radio frequency coils for each band are used as the intermediate frequency coils for receiving the next higher band, the intermediate frequency is maintained at a desired value of substantially onethird the frequency of the lower limit of the band to be covered while utilizing a minimum of additional circuit elements. The performance of a receiver utilizing this system thereby is improved through each of the several bands of a wide frequency range.

I claim as my invention:

1. In a superheterodyne receiver having a plurality of tunable high frequency signal selecting circuits, and a plurality of intermediate frequency amplifier circuits, the combination of means for adjusting the tuning of the intermediate frequency amplifier circuits for differing wave band response corresponding to a predetermined wave band adjustment in said tunable signal selecting circuits, said means comprising a plurality of tunable coupling units supported for progressive insertion in the intermediate frequency amplifier circuits and the signal receiving circuits in adjusting the response of the receiving system from a higher frequency band to a lower frequency band.

2. A radio receiver in accordance with claim 1 further characterized by the fact that the intermediate frequency amplier coupling units for a predetermined frequency band are responsive to a frequency substantially 1/3 of the lowest frequency in a selected signal band of frequencies to be received through the signal selecting circuits.

3. In a multi-wave ceiver, the combination band superheterodyne reof a plurality of tunable signal receiving circuits, a plurality of intermediate frequency amplifier circuits, yand means providing a plurality of coil units for said circuits for each wave band to be covered by said receiver,

said units being supported for progressive insertion in the said receiving circults and said intermediate frequency amplifier circuits, the coils for the intermediate frequency amplifier circuits in one tuning range providing the coils for the signal receiving circuits in the next lower frequency tuning range.

4. In a superheterodyne receiver, the combination of means for selectively adjusting the tuning range of the intermediate frequency and high frequency signal receiving circuits in predetermined fixed `frequency relation to each other through a plurality of differing frequency bands, said means including and being adapted for progressively utilizing a seriesv of progressively insertible tuning units for said circuits, first in an intermediate frequency circuit, and then` in a high frequency signal selecting circuit in the next lower band ofsignal frequencies to be received.

5. In a superheterodyne receiver having a plurality of tunable high frequency signal selecting circuits, and a plurality of intermediate frequency amplifier circuits, a combination of means for progressivelyv changing the frequency response range of said signal selecting circuits in a plurality of differing frequency ranges, means for progressively changing the frequency response of said intermediate frequency amplifier circuits, said signal selecting circuits and said intermediate frequency amplifier circuits each having contacts and a series of tunable coupling units supported for progressive movement in unison between the contacts of said intermediate frequency amplifier circuits and the contacts of the high frequency signal selecting circuits, the intermediate frequency coupling units for a higher frequency receiving range being tuned substantially to the lowest frequency in the next lower frequency receiving range for said signal receiving circuits, whereby said tuning units are progressively operable in the signal selecting and intermediate frequency amplifier circuits.

6. In a superheterodyne radio receiver having a high frequency amplifier and an intermediate frequency amplifier, the combination therewith of means providing a coupling coil system for said amplifiers comprising a series of coupling coil units supported for movement in unison progressively from connection with the intermediate frequency amplifier circuits into connection with the high frequency amplifier circuits thereby to change the tuning range of the receiver, and said tuning units being adjusted to provide a predetermined frequency relation between a selected intermediate frequency and the lowest frequency in the tuning range of the high frequency amplifier circuit throughout the frequency range of operation of the receiver, whereby a desired image frequency ratio between received signal and the in.- termediate frequency is maintained and a predetermined degree of selectivity is provided throughout the tuning range of the receiver.

7. In a superheterodyne receiver, the combina.- tion of a radio frequency amplifier having a high frequency coil system comprising a plurality of movable coil units for adjusting the tuning range thereof, said coil units being lsupported for progressive insertion into and removal from said radio frequency amplifier andan intermediate frequency amplifier therefor having amplifying circuits adapted to receive from the radio frequency amplifier at least one of said tuning units in circuit connection therewith as the frequency determining means therein in at least one higher frequency range of operation following the use of said unit in the preceding higher frequency range for the radio frequency amplifier.

WINFIELD R. KOCH. 

